Mouse p53 represses the rat brain creatine kinase gene but activates the rat muscle creatine kinase gene.

Abstract

The creatine kinases (CK) regenerate ATP for cellular reactions with a high energy expenditure. While muscle CK (CKM) is expressed almost exclusively in adult skeletal and cardiac muscle, brain CK (CKB) expression is more widespread and is highest in brain glial cells. CKB expression is also high in human lung tumor cells, many of which contain mutations in p53 alleles. We bp -195 to +5 of the CKB promoter and within bp -168 to -97 of the CKM promoter. Moreover, a 112-bp fragment from the proximal rat CKM promoter (bp -168 to -57), which contained five degenerate p53-binding elements, was capable of conferring p53-mediated activation on a heterologous promoter in CV-1 cells. Also, this novel p53 sequence, when situated in the native 168-bp rat CKM promoter, conferred p53-mediated activation equal to or greater than that of the originally characterized far-upstream (bp -3160) mouse CKM p53 element. Therefore, CKB and CKM may be among the few cellular genes which could be targets of p53 in vivo. In addition, we analyzed a series of missense mutants with alterations in conserved region II of p53. Mutations affected p53 transrepression and transactivation activities differently, indicating that these activities in p53 are separable. The ability of p53 mutants to transactivate correlated well with their ability to inhibit transformation of rat embryonic fibroblasts by adenovirus Ela and activated Ras.The creatine kinases (CKs) (EC 2.7.3.2) catalyze the reversible transfer of a high-energy phosphate group from creatine phosphate to ADP, thus regenerating ATP in cellular reactions which expend large amounts of ATP, e.g., muscle contraction and ion transport (55). Vertebrates express four distinct CK enzymes which are products of separate, single-copy genes: the brain isoform (CKB), the muscle isoform (CKM), and two mitochondrial isoforms (CKmi). The active form of the cytoplasmic CK is a dimer which exists in three, electrophoretically separable isoforms: MM (predominant form in adult skeletal and cardiac muscle), BB (predominant form in the brain and embryonic skeletal and cardiac muscle), and MB (present in embryonic and cardiac muscle in moderate amounts) (55). The CKmi self-associates to form dimers and octamers located on the outer surface of the inner mitochondrial membrane (55). It has been proposed that the ATP generated in the mitochondrion is used (by CKmi) to generate creatine phosphate, which is subsequently transported to the cytoplasm and used by the cytoplasmic CK (CKB or CKM) to regenerate ATP at sites of high ATP consumption (55).Transcription of CKM is regulated in a highly tissue specific manner, being expressed almost exclusively in skeletal and cardiac muscle (23,24,35,54). In undifferentiated dividing myoblasts, CKM is not expressed and CKB is barely detectable. Early after myoblast fusion, CKB mRNA is transiently expressed and then returns to basal levels, at which time * Corresponding author. Phone: (302) 831-2281. expression of CKM mRNA begins and increases thereafter to allow CKM t...

Ankyrin Repeat and Suppressors of Cytokine Signaling Box Protein Asb-9 Targets Creatine Kinase B for Degradation

“…The CKB gene is positively regulated by the oncogene E1a and negatively regulated by the tumor suppressor gene, p53 (29,32). Also, many growth factors and hormones, such as estrogen, stimulate CKB activity and expression (46,47).…”

“…Furthermore, CKB is induced by the adenovirus E1a oncogene (31). Conversely, wild-type p53 repressed the CKB promoter (32). In fact, many human small cell lung carcinomas, which exhibit elevated CKB expression, contain mutations in p53 alleles (reviewed in Ref.…”

E-Box Sites and a Proximal Regulatory Region of the Muscle Creatine Kinase Gene Differentially Regulate Expression in Diverse Skeletal Muscles and Cardiac Muscle of Transgenic Mice

“…The ⌬1 region also contains VOL. 16,1996 TRANSGENIC ANALYSIS OF MCK E BOXES AND PROXIMAL REGION 5065 p53 activation sites (29,74), as well as an unconserved E box at nt Ϫ98. It would be surprising if the latter E box were functional, because it is not conserved in the rabbit MCK promoter and because a CAT transgene with 117 bp of the mouse MCK promoter has no activity (16).…”

p53-mediated transcription induces resistance of DNA to UV inactivation

“…This region is in¯uential in preserving the correct conformation of the protein and is therefore very sensitive to inactivating mutations (Finlay et al, 1988;Raycroft et al, 1991;. Some of the mutations that we generated a ect transcriptional activity, others do not (Zhao et al, 1994). We therefore introduced these various mutant genes (in pSV.p53) into (10)1 cells along with untreated or UV irradiated pRGC.FOS.CAT.…”